Eugen RochkoHaving been here since 2016, I can tell you there is definitely no such thing as a consensus on usage of content warnings on the fediverse. It's a decentralized network that doesn't belong to any one party, so by definition there is no single culture on it. Different corners have different expectations and customs.
For my part, I've always seen them as something at the discretion of the author. As the reader, you have a plethora of tools to disengage from unwanted content on Mastodon—with even better filters coming in 4.0—and harassment is not one of them. People who are arriving now have as much right to be here and bring their own culture as the ones who came before them.
Jay Arnold 
@Gargron that said, I hope people leaving a toxic environment don’t bring toxic habits with them. I’m more interested in adapting to this more elegant, peaceful environment than trying to make it something else. It’s been a warm welcome here and I appreciate it.
Jenna Wright@jayarnold @Gargron I agree, Jay. I’ve only just created my Acct here, but, I’m committed to leaving behind frenetic communication behaviors that many of us developed in what felt like survival mode at Twitter over the last 6 years. I’ll be focused on building community and solution driven dialogue to tackle some of the more serious issues facing us instead of taking the “red alert, all hands on deck” tweeting approach that I and many others have taken. I aim to be focused & intentional.
MJ@INVR